const fs = require('fs')

function myReadFile(fileName) {
    return new Promise((resolve, reject) => {
        fs.readFile(fileName, 'utf-8', (err, data) => {
            err ? reject(err) : resolve(data.length)
        })
    }).catch((err) => {
        console.log(err);
    })
}

async function abc() {
    let r1 = await myReadFile('./files/a.txt')
    let r2 = await myReadFile('./files/b.txt')
    let r3 = await myReadFile('./files/c.txt')
    console.log(r1);
    console.log(r2);
    console.log(r3);

}
abc()